Thursday, May 28, 2020

ELA & Literacy in Science Middle School Text & Tasks: The Science Behind Ice Cream

In my FUN-YET-EDUCATIONAL reading informational text and tasks lesson that gets students to meet several standards for Reading in Science & Technical Subjects plus Writing, & also having fun learning all about the science behind ice cream (plus the procedure for making their own ice cream), they learn that:

Here are 5 Cool Facts About Ice Cream (students will learn in my lesson):

1. Long before modern refrigeration and freezers, around 200 BC, the Chinese enjoyed a frozen mixture of milk and rice sweetened with syrup. It was made frozen by pouring snow mixed with an ancient salt over the ingredients. Roman Emperors have been known to have snow retrieved from mountaintops in order to create the finest chilled delicacies. The Ancient Greeks, around the year 400 AD, ate snow mixed with honey and fruit in Athens. 
2. Scientifically, ice cream is a complex substance that you would never find in nature. In order to create a smooth, creamy concoction and then freeze it in place, you must use a special technique. You must whip together and freeze the ingredients all at the same time in order to create and suspend the most important ingredient  – air bubbles! Under normal circumstances, if you simply mixed the ingredients in ice cream together, they would quickly separate apart. The fat globules from the milk would rather stick together than be spread out among ice crystals, air bubbles, sweeteners, and flavorings. To truly make it an emulsion, a mixture of liquids in which one liquid is scattered throughout the other but is not dissolved, you can whip up the ingredients to really spread them out. 
3. In addition to being an emulsion, ice cream is also considered a foam. A foam is a light mass of fine bubbles formed in liquid. When the ingredients in ice cream are whipped together, air bubbles get beaten into the mixture. Often in an ice cream maker, a blade will continuously move throughout the mixture to aerate it, or move air through it. Air makes up between a third and a half of the total volume of ice cream! 
4. One key to freezing this foamy emulsion – whether in an ice cream maker or in a plastic baggie – is to freeze it quickly so that the liquid ingredients turn into ice crystals and “trap” all the other ingredients and air bubbles in place. While the ingredients are being whipped together, the liquids will only turn into ice crystals if they are cooled with something that is even colder than ice. That is why rock salt is added to the ice that surrounds the barrel in ice cream machines or in the baggie of ice you can use to make ice cream yourself at home. 
5. Adding salt to ice artificially lowers the freezing point of water. This is called freezing-point depression. The discovery of this principle was a real game-changer in the history of ice cream making. Before this, people had to make do with mixing ingredients with snow and ice to make a chilled delicacy. But once people discovered how to lower the freezing point of liquids (by adding rock salt to ice), they could not only chill their mixture – they could freeze it. And that is how we got ice cream!

So, please get this very thorough, full-of-standards-based-activities, lesson today!

In addition to summarizing central ideas, writing to explain the scientific procedure of how ice cream is made, writing a narrative about an ice cream incident, learning scientific vocabulary, citing evidence, getting the recipe for homemade ice cream in a baggie, and even doing a fun Mad Lib activity about ice cream, students fill out this graphic organizer in the lesson:


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